1. Field of the Invention
The present invention relates to a biaxially blow molding apparatus forming a predetermined shape of molded product by transporting a preform carrier carrying a preform along a transporting path extending across a heating portion and a stretch-molding portion and by performing biaxially stretching blow molding for the preform.
2. Description of the Related Art
A biaxially stretching blow molding apparatus producing resin products, such as PET bottle or so forth, by biaxially stretching blow molding, is constructed to heat a primary molded product which is called as a preform, up to a temperature adapted for molding during transportation across the heating portion, and then perform biaxially stretching blow molding for the preform in a stretch-molding die forming the stretch-molding portion.
A typical biaxially stretching blow molding apparatus has a construction including a preform supply portion, a preform heating portion, a stretch-molding portion and a molded product taking out portion, and continuously or intermittently circulating a plurality of preforms along a guide rail defining a transporting path extending across respective of the foregoing portions. On the other hand, a typical preform carrier has a construction including a slide portion guided by the guide rail to move therealong, and a core portion extending from the slide portion to be inserted into the preform.
The preform is loaded on each preform carrier in the preform supply portion so that an opening mouth of the preform is set on the core portion of the preform carrier. On the other hand, the molded product obtained by performing biaxially stretching blow molding for the preform in the stretch-molding portion is unloaded from each preform carrier by releasing an opening in a neck portion of the molded product from the core portion of the preform carrier in the product taking out portion and collected in a predetermined collecting site. Furthermore, the empty preform carrier unloaded the molded product is returned to the preform supply portion for loading the next preform.
In the biaxially stretching blow molding apparatus having a construction to support the preform by the preform carrier which is continuously transported along the predetermined circulating path, it has been strongly demanded to speeding up operation at respective portions for improving overall process performance and whereby for improving cost effectiveness.
On the other hand, the preform carrier unloaded the molded product after passing through the stretch-molding portion is schematically returned to the preform supply portion again by-passing the stretch molding portion. When the by-pass passage for the empty preform carrier can be formed through a dead space below the stretch-molding portion, the circulating path may be constructed in compact. In such case, height difference is caused in the circulating path to require transfer of the preform, the molded product and the preform carrier between the transporting paths having height difference. If transfer operation can be done efficiently, process speed of the biaxially stretching blow molding apparatus can be improved.
Next, the preform transported by the preform carrier along the circulating path is formed into the molded product which has greater width and greater height in comparison with the preform in the stretch-molding portion. Therefore, it becomes necessary to provide greater feeding pitch of the preform carrier on the upstream side of the stretch-molding portion. If transporting operation for the preform carrier can be done efficiently by converting operation of the feeding pitch and with widened feeding pitch, process speed of the biaxially stretching blow molding apparatus can be further improved.
On the other hand, a mold clamping mechanism which opens and closes a pair of stretch-molding dies in order to perform stretch-molding of the preform, generally has a construction to open and close each stretch-molding dies which are slidably supported, by means of an air cylinder via a toggle link mechanism. If opening and closing operation of the stretch-molding dies by the mold clamping mechanism can be done efficiently, process speed of the biaxially stretching blow molding apparatus can be further improved.
The present invention has been worked out in order to satisfy demands set forth above. Therefore, it is an object of the present invention to provide a biaxially stretching blow molding apparatus which has high process speed by improving efficiency of operation in respective components.
Another and more particular object of the present invention to provide a biaxially stretching blow molding apparatus which can efficiently perform transfer operation of a preform, a molded product and a preform carrier between transporting paths having height difference.
A further object of the present invention is to provide a biaxially stretching blow molding apparatus which can efficiently perform an operation for expanding a feeding pitch of the preform carriers on upstream side of a stretch-molding portion and a transporting operation of the preform carrier with the expanded feeding pitch.
A still further object of the present invention is to provide a biaxially stretching blow molding apparatus which can efficiently perform mold clamping operation of a pair of stretch-molding dies for performing biaxially stretching blow molding.
In order to accomplish the above-identified and other objects, according to the first aspect of the present invention, a biaxially stretching blow molding apparatus perform biaxial stretch-molding for a preform into a predetermined shape by transporting a preform carrier supporting the preform along a transporting path extending across a heating portion and a stretch-molding portion, comprises:
first and second reversing means for reversing the preform carrier;
first and second transporting paths forming the transporting path;
the first reversing means receiving the preform carrier transported in up-side-down position along the second transporting path, reversing the received preform carrier into elected position, and transferring the preform carrier thus reversed to the first transporting path; and
the second reversing means receiving the preform carrier transported in elected position along the first transporting path, reversing the received preform carrier into the up-side-down position, and transferring the preform carrier thus reversed to the second transporting path.
In order to make the first and second transporting paths compact, it is preferred that the first transporting path is an upper transporting path extending across a stretch-molding position of the stretch-molding portion, and the second transporting path is a lower transporting path extending lower side of the stretch-molding portion. With this construction, in comparison with the case where the second transporting path is arranged by-passing the stretch molding portion having largest dimension in the width direction in lateral direction, the biaxially stretching blow molding apparatus can have compact construction.
On the other hand, it is possible that at least one of the first and second reversing means has a pivoting member pivoting about a predetermined pivot center and a pair of preform holding portion formed at symmetric positions of the pivoting member with respect to the pivot center. In this case, it is desirable that one of the preform holding portions being placed at a height corresponding to the upper transporting path and the other preform holding portion being placed at a height corresponding to the lower transporting path at pivot stop position of the pivoting member.
With the construction set forth above, whenever the pivoting member is pivoted, both of the preform carrier holding portions are respectively positioned at the height positions corresponding to the upper and lower transporting paths. Therefore, transfer of the preform carriers between respective preform carrier holding portions and the upper and lower transporting paths can be done efficiently.
Here, the preform holding portion may have a guide groove, into which the preform carrier can be inserted in lateral direction in a condition not withdrawn in vertical direction. On the other hand, the preform carrier may have a slide portion sliding along the transporting path and being inserted into the guide groove, and a core projecting from the slide portion for inserting into the preform.
The biaxially stretching blow molding apparatus may further comprise a preform supply portion. The preform supply portion may comprise:
the first reversing means having the pivoting member and the preform carrier holding portion;
preform inserting means for loading an opening portion of the preform from lower side to the core of the preform carrier held in up-side down position in a guide groove of one of the preform carrier holding portions in the first reversing means; and
feeding out means for feeding out the preform carrier held in elected position with supporting the preform in the guide groove of the other preform carrier holding portion of the first reversing means.
With the preform supply portion constructed as set forth above, while operation for receiving the empty preform carrier in one of the preform carrier holding portions, preform loading operation for the preform carriers and transferring of the preform carriers supporting the preforms to the transporting path are performed on the side of the other preform carrier holding portion. Since mutually different operations are performed simultaneously in both of the preform carrier holding portions, operation of the preform supply portion can be efficient to enhance process speed of the biaxially stretching blow molding apparatus.
Here, it is desirable that the preform supply portion has a drop preventing means for preventing dropping of the preform loaded on the core of the preform carrier by the preform inserting means from the core.
On the other hand, by arranging the preform carrier holding portions at symmetric positions relative to the reversing shaft as a center of the pivoting member, complete balance in weight can be established to contribute for speeding up reversing operation.
Next, the biaxially stretching blow molding apparatus has a molded product taking out portion. The molded product taking out portion may comprises:
the second reversing means having the pivoting member and the preform carrier holding portion;
a pair of gripping pieces gripping neck portions of the molded products from both sides loaded on the preform carriers respectively held in the preform carrier holding portion;
gripping piece opening and closing means for moving the gripping pieces between a molded product gripping position and a molded product releasing position;
molding product removing means for removing the core of the preform carrier from the neck portion of the molded product gripped by the gripping pieces;
a pair of guide plates which can be guided in a horizontal direction with supporting the neck portions of the molded products loaded on the preform carriers respectively held in the preform carrier holding portion;
guide plate opening and closing means for moving the guide plates between a guiding position of the molded product and a molded product releasing position retracted from the guiding position.
In the molded product taking out portion constructed as set forth above, while operation for receiving the preform carrier supporting the molded product in one of the preform carrier holding portion, withdrawal of the molded products from the preform carriers and feeding out of the emptied preform carriers are performed in the other preform carrier holding portions. Since mutually different operations are performed simultaneously in both of the preform carrier holding portions, operation of the molded product taking out portion can be efficient to enhance process speed of the biaxially stretching blow molding apparatus.
Herein, it is desirable that the molded product taking out portion comprises detecting means for checking good item and no-good item of the molded product supported by the preform carrier; and control means for controlling opening and closing of a pair of the pair of gripping pieces and the pair of guide plates on the basis of result of checking by the detecting means and controlling opening and closing of a pair of the pair of gripping pieces and the pair of guide plates when the preform is supported without being blow molded.
On the other hand, similarly to the preform supply portion, by arranging the preform carrier holding portions at symmetric positions relative to the reversing shaft as a center of the pivoting member, complete balance in weight can be established to contribute for speeding up reversing operation.
According to the second aspect of the present invention, a biaxially stretching blow molding apparatus perform biaxial stretch-molding for a preform into a predetermined shape by transporting a preform carrier supporting the preform along a transporting path extending across a heating portion and a stretch-molding portion, comprises:
a pitch expansion mechanism for expanding a feed pitch of the preform carriers fed into the stretch-molding portion and feeding out from the stretch-molding portion,
a transferring mechanism for feeding said preform carrier into said stretch-molding portion and for feeding out said preform carrier from said stretch-molding portion by said pitch expansion mechanism.
the pitch expansion mechanism including first and second holding members simultaneously holding at least first and second preform carriers transported along the transporting path in lateral direction, holding member moving means for expanding an interval between the first and second holding members, in which the preform carriers are held, and holding member moving means for moving the first and second holding members between a preform holding position and a retracted position retracted from the preform holding position, and
the transferring mechanism including a holding plate holding the first and second preform carriers from lateral direction after expanding the pitch, holding plate moving means for moving the holding plate between a preform holding position and a retracted position retracted from the preform holding position, and holding plate feeding means for moving the holding plate along the transporting path for feeding the first and second preform carriers which is expanded the pitch therebetween into the stretch-molding portion and feeding out from the stretch-molding portion.
In the biaxially stretching blow molding apparatus constructed as set forth above, pitch expanding operation and transporting operation of the preform carrier with the expanded pitch are performed separately and independently of the other. Accordingly, in comparison with the case where both operation are performed with the single mechanism to perform these operation more quickly to result in higher process speed of the biaxially stretching blow molding apparatus.
According to the third aspect of the present invention, a biaxially stretching blow molding apparatus perform biaxial stretch-molding for a preform into a predetermined shape by transporting a preform carrier supporting the preform along a transporting path extending across a heating portion and a stretch-molding portion, comprises:
the stretch-molding portion having a pair of stretch-molding dies and a claming mechanism for opening and closing the stretch-molding dies;
the clamping mechanism comprising:
a first toggle link mechanism for moving one of the stretch-molding dies between an opening position and a closing position;
a second toggle link mechanism for moving the other the stretch molding die between an opening position and a closing position; and
a swing mechanism for reciprocally moving the first and second toggle link mechanism at respective link connection points in opposite direction in synchronism with each other.
The swing mechanism comprises swing member, first and second end portions of the swing member located at symmetric position about swing center, and first and second connecting members connected to respective link connection points of the first and second toggle link mechanisms.
With the clamping mechanism constructed as set forth above, since die opening operation and clamping operation of a pair of stretch-molding dies can be performed with complete synchronization with the other, these operation can be done efficiently. On the other hand, the first and second toggle link mechanism are moved in mutually opposite directions. Also, load to be exerted upon clamping and opening of dies can act symmetrically about the center of swing motion, local concentration of the load upon clamping or die opening may not act. Furthermore, no impact force may be exerted. Accordingly, these operation can be done smoothly. Thus, since clamping and die opening can be done smoothly, clamping operation and die opening operation can be done quickly and smoothly to result in higher process speed of the biaxially stretching blow molding apparatus.